Remote-control system



Oct. 11, 1949. w D 7 2,484,208

REMOTE- CONTROL SYSTEM Filed March 27, 1947 3 Sheets-Sheet 1 Dispa fching 'ce Superwlfory and Conffo Egu/pm en 2:

WITNESSES: INVENTOR I. M'lla rd/Z Der/t We m' ATTORN Oct. 11,1949. I w,DERR 2,484,208

REMOTE-CONTROL SYSTEM Filed March 27, 1947 3 Sheets-Sheet 2 Subafaf/on XEl/per v/b'or y an d Con fro E u/krn er) 7.

5055/01 0 77 I and Canf/o/ E domen 7".

INVENTOR Oct. 11, 1949.

w. A. ERR

REMOTE-CONTROL SYSTEM Filed March 27. 1947 3 Sheets-Sheet 3 I N VE NTO RMY/Qra Alfie/r:

ATTORN Patented Oct. 11, 1949 REEID'EE-CONTROL SYSTEM Willard A. Derr,Wilkinsburg, Pa., assignor to 'Westinghouse Electric Corporation, EastPittsburgh, Pa, a corporation of Pennsylvania Application March 27,1947, Serial No. 737,661

10 Claims. 1

My invention relates, generally, to remote control systems, and it hasreference in particular to combined supervisory control and remotemetering systems of the multiple station type.

Generally stated, it is an object of my invention to provide an improvedremote control and metering system which is simple and inexpensive tomanufacture, and which is easy to operate.

More specifically, it is an object of my invention to provide forobtaining selective continuous metering over the signal channel of asupervisory control system of the multiple station type.

Another object of my invention is to provide for using a plurality ofmetering transmitters at remote stations in a multiple stationsupervisory control system for selectively operating their respectivereceivers at a dispatching ofiice.

It is also an important object of my invention to provide for normallymaintaining a predetermined value of signal channel impedance byshunting the transmitters and receivers connected to the signal channelof a supervisory control system and for selectively removing the shuntsfrom associated transmitters and receivers when a metering indication isdesired.

It is a further object of my invention to provide for using a seriescircuit signal channel for both supervisory control operations and forremote metering, so as to readily permit supervision of the signalchannel.

Yet another object of my invention is to provide a selective remotemetering system which will operate over supervisory control signalchannels having loop resistances as high as 5,000 ohms.

Another important object of my invention is to provide for continuousselective remote metering from a plurality of remote stations in amultiple station supervisory control system.

Yet another important object of my invention is to provide forcontinuous telemetering over the signal channel of a supervisory controlsystem without the metering equipment causing any variation of thechannel impedance during a supervisory or control operation.

Other objects will in part be obvious, and will, in part, be explainedhereinafter.

In practicing my invention in one of its forms, the signal channel of amultiple station supervisory control system is arranged for connectingthe line relays and impulsing relays at the different remote stations inseries circuit relation with the line relay and the impulsing relay atthe dispatching ofiice. Metering transmitters for current, voltage,etc., are arranged for connection 2 in series circuit relation with thesignal channel at certain control points of the different stations.Corresponding metering receivers are arranged likewise at thedispatching ofilce. The transmitters and receivers are normally shuntedso as to maintain a predetermined value of signal channel impedance forsupervisory control operations. The shunts are selectively removed froma particular transmitter and its corresponding receiver upon theselection of the desired metering point from the dispatching office. Thetransmitters and receivers are so controlled that a supervisory orcontrol signal occurring during a metering operation effectively shuntsand/or disconnects the transmitters and receivers from the signalchannel until the supervisory control operation is completed. Thedifierent metering points at the dispatching office are so interlockedthat a second metering point may not beselected while ameteringoperation is taking place.

For a more complete understanding of the nature and scope of myinvention, reference may be made to the following detailed descriptionwhich may be studied in connection with the accompanying drawings, inwhich:

Figure 1 is a diagrammatic View of the dispatching offlce supervisoryand control equipment in a multiple station system embodying myinvention in one of its forms;

Fig. 2 is a diagrammatic view of the supervisory and control equipmentat two remote stations connected with the dispatching oifice of Fig. 1;and

Fig. 3 is a simplified diagrammatic View of the signal channel and theassociated supervisory control and metering equipment used in connectionwith the system of Figs. 1 and 2.

The preferred embodiment of the invention is shown and described hereinfor purposes of illustration as it may be applied to a supervisorycontrol system of the type disclosed in Patent No. 2,059,284 whichissued on November 3, 1936 to H. P. Boswau. For convenience ofdescription, and in order to refrain from unnecessarily confusing theinvention with the more or less involved circuits of the Boswau patent,the supervisory and control equipment at the dispatching office whichcomprised Figs. 1 through 4' of the Boswau patent has been representedgenerally by a single enclosure in 1 of the drawings in the presentinstance. The supervisory and control equipment of Figs. 5, 6 and 'I ofthe Boswau patent has been represented by the single enclosure atsubstation A of Fig. 2, and an additional substation X has been addedwith similar equipment in order to fully illustrate the app cation ofthe invention to a multiple station system. Fig. 3 has been patternedafter Fig. 10 of theBoswau patent, but with the designations of Figs. 1and 2 used, instead of those of the Boswau patent.

All of the equipment of the Boswau patent which has not been-changed inany respect remains within the enclosures and is not illustrated indetail. All of the equipment of the Boswau patent to which any changeshave been made has been shown as viewed through windows in theenclosures. wau patent shown in Figs. 1 and 2 bear the same referencecharacteristics as in the Boswau patent drawing. All additionalequipment is shown as" superimposed on the main enclosure, and isdesignated by reference characters which are not found in the Boswaupatent.

Referring generally to Figs. '1 and 2 of the drawings, the referencenumeral It] of Fig. 1 may designate generally an enclosure whichrepresents thesupervisory control equipment at the dispatching office ofa multiple station system,

such as is described in detail in the Boswau pat ent hereinbeforereferred to. The reference numerals i2 and I4 of Fig. 2 of the drawingsdesignate enclosures which represent the supervisory and controlequipment at two of the remote substations A and X, respectively, whichmaybe aS- sociated in amultiple station system with the dispatchingofiice of Fig. 1.

It will be seen that the first control point at the dispatching officeof the Boswau patent, which was usedto control a circuit breaker at oneof the remote stations, has been arranged for controlling a meteringpoint I5 of the supervisory control equipment l2 at substation A,wherein a me tering relay l 6 has been substituted for the close andtrip relays l3!) and 13!. The second con- 3 trol point at thedispatching office, which was ilapparent that the signal channel hasbeen arranged to provide a series circuit such as shown in Fig. 10 ofthe Boswau patent, with the exception that. the line battery source IIis at the remote The line relay 5H at substation A are connected inseries circuit relation with armatures 430a and fillla of the impulsingrelays 430 and 5"), respectively.

,For purpose of simplification, the supervisory and control equipment atthe second substation patent, has been designated by primed numeralscorresponding to the designations of similar equipment at substation A.The line relay 5! I the signal channel. The invention has beenillustrated with the metering relay [5 energized to 1 connect'themetering point [5 for a metering operation, so as to correspond with theshowing of i the equipment in the Boswau patent.

- In order to provide a metering indication at the dispatching officefrom the point l5. atsub- The elements of the system of the BosstationA, a metering transmitter may be provided at substation A comprising acurrent transformer 2!}, which may be used in connection with anauxiliary transformer 2! for applying an alternating current voltage toa full-wave rectifier transmitter device 22. The rectifier 22 may beconnected in series circuit relation with the si nal channel conductors432 and 433, for applying thereto a voltage which is proportional to thevalue of the current measured by the transformer value when not meteringand thus improving sig- X, which is'not shown in detail in the Boswau 1and armature 5ill'a at substation X may likewise be connected in seriescircuit relation with nal conditions, the metering relay l 6 may be usedfor providing a circuit to normally shunt the rectifier 22 from thesignal channel. Armature Ifig of the metering relay may be used for thispurpose. The current transformer 20 may be disconnected from theauxiliary transformer 2| through armatures Hie and Hi) When the meteringpoint is not in operation. An additional armature I6d may be used toshort circuit the current transformer 26 to prevent a dangerously highopen circuit voltage from being developed.

Control of the metering point may be effected by connecting the meteringrelay It to the supervisory control equipment through armatures 148 andI49 of the point relay H4. The close conductor which is energizedthrough armature 148 from the substation battery may be connected to oneterminal of the metering relay l6 and to armature ltb whose frontcontact is connected to direct positive. 'By connecting the otherterminal to negative through a resistor l3, operation of the meteringrelay is may be effected to connect the rectifier 22 in series circuitrelation with the signal channel conductors 432 and 433 when a closeoperate code is transmitted from the first point of the dispatchingoffice. Likewise, by connecting the trip conductor which is energizedthrough armature 149 of the point relay, to said other terminal, themetering relay will be shunted down to effectively disconnect therectifier 22 from the signal channel when a trip code is transmitted.Armature H4a of the point relay H4 may be utilized to connect therectifier 22 in circuit relation with the signal channel conductors whenthe metering point is selected, so that the channel may be calibratedfor metering, as will be hereinafter explained in detail. In order toprovide for continuous telemetering and yet give preference tosupervisory and control signals originating at either the dispatchingoifice or any of the control points at the remote substations, provisionmay be made for disconnecting the rectifier 22 from the signal channeland rendering it ineffective whenever such a supervisory or controlfunction is commenced. For this purpose, the rectifier may bedisconnected from the auxiliary transformer 2| by either armature 5l4bof the receiving or start prevent relay 5H3, or armature 5I6b of thestarting relay 5l8. At the same time, armatures M40 and "5160 of theserelays may be used to shunt armature l6g of the metering relay so as toeifectively shunt the rectifier 22 from the signal channel and restorethe normal signal impedance nel conductors through the same rectifier22. The transformer 25 may be connected to the auxiliary transformer 21by means of armatures Nd and He of the metering relay ll. The meteringrelay il may be controlled through armature H511, of the point relay H5,in a manner similar to that described hereinbeiore in connection withthe metering relay it, for actuating arma ture llj which is connected incircuit relation with armature leg, to connect the rectifier 22 incircuit relation with the signal channel. Armatures Eldd and SlEid ofthe start prevent relay 5M and the starting relay 545, respectively, ofthe supervisory control equipment may be used to shunt armature ll) ofthe metering relay 5?, for shunting the rectifier from the signalchannel whenever a supervisory or control operation is commenced fromanother control point, while metering relay ii ope ated during a meering operation from the control point lfi.

It will be seen that the metering arrangements at the remote controlpoint at so. station I; may be similar to those for the control pointsat substation A. For example, a rectifier 2? may be arranged forconnection in series circuit tion with the signal channel conductors 332a d 333 by a metering relay 2% which removes a shunt across therectifier through armatiu'e 286 win on it is energized. The rectifiermay be energised from a potential transformer through an auxiliarytransformer 32. The metering relay 2% may be arranged to normally shuntthe output cir uit of the rectifier 2'! through armature 28s. rileauxiliary transformer 32 may be connected to the potential transformertil through armatures 28c and 28d.

The metering relay 28 may, as hereinbeiore described, also be arrangedfor operation in response to the close and trip codes transmitted fromthe dispatching oiilce through the close and trip circuits of the Boswaupatent which are set up through armatures l l ia and l i ib of the pointrelay ll l. T--e shunt across the rectifier circuit may be removed fcalibration poses by connecting armature of the point relay in seriescircuit relation with armature 2%.

As described in connection with the equipment at substation A, thereceiving or start prevent relay 5% may be arranged to shunt the outputcircuit of the rectifier through armature El te and front contactwhenever an incoming supervisory or control is received. The start relay535' may be arranged to shunt the output circuit of the rest circuit 2!through arma ture 545's and front contact in case a super visory orcontrol operation initiated from another point at subst ion The inputcircuit of the rectifier 2'5 may be interrupted under these conditionsby a tures Elt'b and iilB'b, respectively.

At the dispatching office, as shown in Fig. 1, a suitable metering1.,C-SlV6I may be associated with the first point for operation inresponse to the output voltage of the rectifier 22 when the remotemetcri.. point i5 is selected. The receiver 33 may be connected inseries circuit relation with the channel conductors 532 and Q33 and theline relay 63$ the office. In order to provide for normally blocking thereceiver 3-3 from the channel, armatine i liic of the supervisory pointrelay H6 may be arranged for normally shunting the receiver when thispoint is not operating, and the relay I H] is in the deenergizedposition.

For the purpose of calibrating the receiver to existing signal channelconditions, armature l "id of the individual point relay ll 5 may beconnected in series circuit relation with the armature Hile so as toconnect the receiver 33 in series circuit relation with the channelconductors 432 and 533 the individual point relay i it operates upon ptof the point selection check code from the remote substation A. Meanssuch as the potentiometer 34 and the bridge circuit 35 may be providedfor inserting a variable reversible calibrating voltage in circuitrelation with the channel conductors to calibrate the signal channel andprovide a zero value of line current of 5 milliamperes, for example, inorder to zero the receiver 33 without varying the effectiveimpedance ofthe channel.

In order to provide for efiectively blocking the storing receiver 33from the signal channel during a supervisory or control operation whichmay be initiated during a metering operation, provision may be made forshunting the armature lite of the supervisory point relay i For example,armature ABZI of the receiving start relay 402 may be connected in shuntcircuit relation with the armature l lile, since the receiving startrelay picks up immediately upon the receipt of any super-- visory signalfrom any one of the remote stations. Armature 4841) of the sending startrelay 5% may be connected in parallel circuit relation with the armature482 for shunting the metering receiver 33 whenever a supervisory orcontrol operation is initiated from the dispatching office during ametering operation Additional metering receivers 31 and 38 may beprovided at the second and third control points of the dispatchingoflice for operation in response to metering signals transmitted fromthe remote metering points i3 and lilat the remote substations A and X,respectively. The metering receivers 3i and 38 may also be connected inseries circuit relation with the signal channel conductors 132 and 433and receiver 33. The supervisory point relays Ill and l l2 associatedwith these ponts may be used to control the connection of the receiversi M and H5 through armatures H to and 2e, respectively, which shunt thereceivers when the relays are in the deenergized position.

The receivers 31 and 38 may be connected in series circuit relation withthe signal channel conductors upon the selection of their respectivemetering points by means of armatures I ltd and Mid of the individualpoint relays H6 and iii associated with the respective control points,so as to provide for calibrating the signal channel for meteringoperations. Provision may also be made for effectively disconnecting thereceivers ill and 38 from the signal channel upon the initiation ofsupervisory or control operations from any oi the control points bymeans of armatures ittle, illild and front contacts of the receivingstart relay 692, and armatures tilde, 46401 of the sending start relay404, which parallel armatures l ltd and l l'ld, respectively, in amanner similar to that described in connection with the meteringreceiver 33.

Since it is generally undesirable to permit the initiation of a secondmetering operation while is already taking place, means may provided atthe dispatching oflice for interlocking the metering control points ofthe different remote substations. For example, the operating circuitscontrolled by the operating key 10'! of the first control point and theoperating key 4!! of the second point, which was shown but notidentified in the Boswau patent, may be passed through armatures 2c, 2dand back contacts of the individual point relay 2 of the third controlpoint. This means that if an attempt is made to select'either themetering point or the point H3 at the substation A, when the meteringpoint l9 at substation X is being used for a metering indication, theoperating keys I01 and will be ineffective to select the points l5 andI8.

Likewise, by utilizing armatures H00, H lo, and lid, Hid in circuitrelation with the operating key 4! of the third control point for thecontrol of the metering point as at substation X, the operating keythereof may likewise be rendered inoperative if a metering operation istaking place from either the control point [5 or the control point it atsubstation A. Interlocking between the two control points l5 and [8,which are both at substation A, may be provided by connecting theoperating circuits for the meter relays l6 and H through armatures Ilaand armatures [6a, respectively.

In order to provide for line supervision of the signal channel, meanssuch as the line supervision relay 43 may be utilized. The linesupervision relay may be of the slow release type, and may be connectedto a suitable source of control potential in circuit relation with thearmature 43Ib of the line relay 43!. Since the signal channel isnormally energized, and the line relay is normally in the energizedposition, the line supervision relay 43 will likewise be normallymaintained in the energized position. The line supervision relay may beused to control an alarm relay l5 over armature 43a for effectingoperation of an alarm i5 and lighting a line supervision lamp ll overarmatures a and 4517 when the alarm relay is deenergized for apredetermined length of time, such as might be caused by the failure ofthe station battery, or a fault onthe signal channel.

The supervisory control system is, as has been stated, shown with themetering relay I6 at point l5 energized to connect the rectifier 22 inthe signal channel. This is in accordance with the showing of the Boswaupatent.

In operation of the system the operator" may desire to remove themetering point I5 from the channel. He therefore actuates the operatingkey [ill of the first control point at the dispatching office, to selectthe metering point l5 at the remote substation A. The sending startrelay 854 at the dispatching office and the receiving or start preventrelay 5 l 4 at substation A pick up on the first pulse. Relay Bi l" atsubstation X also picks up. From the line diagram shown in Fig. 3 itwill be seen that the receiver 33 at the dispatching oflice andrectifier 22 at substation A are thereupon shunted by armatures 40% and5M0, respectively. 7

The station selection, group selection and point selection codes aretransmitted in substantially the manner described in the Boswau patenthereinbefore referred to. Since the receiver 33 and rectifier 22 areshunted from the signal channel the signal channel impedance will benormal, and the supervisory and control operaindividual point relay H5at the dispatching office picks up and sets up a shunting circuit forthe supervisor point relay H0 over armature I66.

The operator then transmits a control code by operating the control keyN33 to the oil posi-' tion. Upon receipt of the operation code, theproper circuit is completed at substation A, through armature 149 of thepoint relay H4, for applying positive to shunt down the metering relayHi. When the relay l6 returns to the deenergized position, armature Higparallels armature 5| ic, and auxiliary point supervisory relay 128 isdeenergized, momentarily interrupting the energizing circuit of thepoint supervision relay at armature 139. This results in a supervisioncode being transmitted to the dispatching oifice to indicate that themetering point l5 has been efiectively disconnected. The disconnectionis effected by armature ifig paralleling armature Side and preparing ashunt for the output circuit of the rectifier 22 to block it from thesignal channel, and by armature 65c and it disconnecting the currenttransformer is from the auxiliary transformer 25. Armature Hie shuntsthe current transformer 28 to prevent a dangerously high open circuitvoltage from being produced.

At the dispatching office the supervisory point rela l i ii is shunteddown upon the receipt of the supervisory code from the remote station tocomplete the shunt across the receiver 33. The operating circuit for theon signal light 262 is interrupted by armature 52?, which now providesan energizing circuit for the off signal light N36. The receiving meter33 is effectively shunted from the signal channel by armature lite whichreturns to the deenergized position.

After completion of the supervisory code, the supervisory equipment isrestored to normaI by the customary long pulse. The point relay 5E4drops out and completes the shunt across the rectifier 22 througharmature ll ia.

Should the operator now desire to select the remote metering point H8 atsubstation A, the operating key 49 may be actuated to transmit theproper station, group and point selection codes in the usual manner forselecting the metering point 98. The point relay H5 at substation Aoperates on receipt of the proper point selection code to connect therectifier 22 in the signal channel at armature a, and set up anoperating circuit for the metering relay i? through armature lltb. Uponreceipt of the point selection check code at the dispatching 0ffice, theindividual point relay lit is energized, and opens armature lied fromits back contact so as to connect the metering receiver 31 in seriescircuit relation with the line conductors 432 and 33. The receivingmeter 31 may now be zeroed by Operating the potentiometer 3 1 as in thecase of the meter 35.

After calibration, the operator actuates the control twist key 45 of thesecond control point to transmit the on or close control code. Uponreceipt of the control code at the substation, the energizing circuitfor the metering re lay ill is completed, and the relay operates,connecting the potential transformer 25 to the auxiliary transformer 2ithrough armatures lid and lie and front contacts. At the same time,armature llf is actuated to insure removal of the shunt from the outputcircuit of the rectifier 22 for substantially the duration of themetering operation, thus effectively connecting it in series circuitrelation with the line conductors 432 and 433. The rectifier 22 of themetering transmit- 9 ter and the metering receiver 31 are now bothconnected in circuit with the line conductors for efiecting a continuousmetering operation.

Operation of the metering relay I! energizes the auxiliary pointsupervision relay lill, causing momentary interruption of the energizingcircuit for the point supervision relay J26. Accordingly, a supervisioncode is transmitted to the dispatch-- ing office to show that themetering point is connected to the signal channel. Receipt of thesupervision code efiects operation of the point su pervisory relay Illwhich insures removal of the shunt from the receiver 31, forsubstantially the duration of the metering operation, and locks in todirect positive.

Operation of the point supervisory relay iii interrupts the energizingcircuit for the off signal lamp and completes an obvious energizingcircuit for the on signal lamp 52. After a predetermined interval o."time, a relatively long pulse is transmitted over the signal channel, inthe manner described in detail in the Eoswau patent hereinbeiorereferred to, and the supervisory control equipment is reset, clearingthe channel for metering operations. Since the point supervisor relay H]is locked into direct positive it is unaffected by the relatively longpulse, as is also the metering relay .l'i, Accordingly, e sienal channelis connected for continuous metermg.

Should a supervisory or control function initiate from any one of theother control points at either the dispatching ofiice or at one of theremote stations, it is generally desirable that the signal channel bemade available therefor. Accordingly, should a supervisory signaloriginate, for example, from some other control point at substation A,the receiving start relay 4E2 Of the supervisory control equipment atthe dispatching ofiice will pick up and remain in the energized positionuntil the termination of the operation. Operation of the relay 4t2effectively shunts the metering receiver 3? over armature 4822c and itsfront contact.

At substation A, the starting relay 5L6 will immediately pick up uponthe initiation of the supervisory signal. This efiectively disconnectsthe metering transmitter from the signal channel, since the outputcircuit of the rectifier 2'2 is shunted by armature 5150 and its frontcontact. At the substation X, the receiving or start prevent relay Sitpicks up upon the receipt of a supervisory signal to perform a similarfunction should the control point Ill be connected for metering insteadof the control point 18.

Should the operator attempt to select the metering point 45 while themetering point it is in operation, the point may be selected, butoperation of the metering relay it cannot be afiec-ted in response tothe transmission of the on or close code, since the operating circuitfor the metering relay .16 must he completed through armature Ha or themetering relay H which is in the energized position Accordingly, thepoint supervisory relay I cannot be momentarily deener ized and thesupervision code for showing the on condition of the meteringtransmitter cannot be transmitted. The operator will thus be advised ofthis condition by the disagreement lam-p remaining lit instead of the onlamp lighting up. The reset button shown in the Boswell patent willthereupon have to be actuated to clear the system and restore it tonormal.

From the above description and the accompanying drawing, it will beapparent that i have pro- 10 vided a supervisory control and remotemetering system which is operable with a plurality of re mote stations.A system embodying the features of my invention may be readily used forselective continuous telemetering from any one of a number of remotestations without interfering with the receipt of supervisory signals orthe operation or remoteequipmentfromothercontrolpoints. By automaticallyrestoring the normal signal imped- 1GB of the signal channel whenever asupervisory or control operation takes place, reliable and efficientoperation of the supervisory control equipment may be affected. Byproviding for calibrating the signal channel for metering operationswithout varying the effective impedance of the signal channel,consistent and reliable operation or the system is facilitated.

ce certain changes may be made in the above described construction anddifferent embodiments of the invention may be made without departingfrom the spirit and scope thereof, it is intended that all of the mattercontained in the above description and shown in the accompanyingdrawings shall he considered as illustrative and not in a limitingsense.

I claim as my invention:

1. In a supervisory control system having a signal channel with a normalsignal impedance connecting a plurality of remote stations and adispatching ofiice in a common series circuit re:- lation with eachother and a plurality of control points at the dispatching ofilce havingcorresponding control points at rlifiei'ent ones or" the remotestations, metering means associated with certain or the dispatchingoffice and remote station points arranged to be selectively connected inseries circuit relation with the signal channel, and control meansresponsive to the initiation of a supervisory control signal fromanother of said points effective to remove the metering means i'com saidseries circuit relation and restore the normal impedance of the signalchannel.

2. In a supervisory control system having asingle series type signalchannel connecting super. visory control equipment at a dis-patchingoilice and a plurality of remote stations with a plurality ofcorresponding control points, meter transmit.- ting means and receivingmeans associated with certain of the points at the substations and thedispatching oilice for selective connection in series circuit relationwith the signal channel for continuous metering, whereby the impedanceof the signal channel is varied from a normal value, and control meansresponsive to a supervisory signal operable to remove said transmittingand receiving means from the signal channel during a supervisory signalfrom certain others of the control points and restore the impedance ofthe signal channel to a normal value.

3. In a multiple station supervisory control system having supervisorcontrol equipment with plurality of control points at .a dispatchingofnce and a plurality of remote stations connected in series circuitrelation by a signal channel having a normal signal impedance, meteringtransmitting means at certain of said points at the remote stationsoperable to produce control voltages proportional to quantities to bemetered, metering receiving means at corresponding points at thedispatching ofiicc responsive to said voltages, circuit means at saidcertain points at the dispatching ofiice and remote stations selectivelyconnecting the metering receiving means and the metering transmittingmeans of one of said .certain points at the dis-patching ofiice and thecol series circuit signal channel to its normal impedance.

fl, In a supervisorycontrol system having a plurality of remote stationsand a dispatching ofiice each having a line relay and impulsing meansconnected in a common series circuit relation by a signal channelhavinga predetermined normal signal impedance, said stations and dis patchingofiice having control points for controlling their respective impulsingmeans to operate. said line relays, metering transmitting means atcertain of the points at different ones of the remote stations, meteringreceiving means at, the dispatching'office, means responsive to theselection of any one of the control points operable to connect themetering transmitting means at said point and the corresponding,metering '7. In a supervisory control system having a plurality ofremote stations and a dispatching office connected by a series circuitsignal channel;

and having a plurality of corresponding control points, a meteringtransmitter associated with certain of the control points atdifferentones of the remote stations, a metering receiver associatedwith the corresponding control points at the dispatching office, meansoperable from said corresponding control points at the dispatchingofiiceto selectively connect one of the metering re:

ceivers in circuit relation with the channel, means at the dispatchingoffice to adjust the effective channel current Without varying thechannel. impedance, control means operable in response to;

a predetermined signal ,frorn vthe dispatching office to connect thecorresponding metering transmitter in circuit relation with the signalvchannel, and means responsive to a supervisory or control operationoperable to shunt the meterreceiving means at the dispatching ofiice inseries circuit relation in the signal channel, and means responsive tothe initiation of a supervisory signal from other of the control pointsthan those associated with the metering means operable to remove themetering means from the signal channel and restore the series circuitsignal channel to its normal impedance so long as the supervisory signalcontinues.

5. In a supervisory, control system having supervisory control equipmentat each of a plurality of remote stations and a dispatching oficeincluding a plurality of control points connected by a seriesltypesignal channel, metering transmitting means at certain of. the controlpoints at different ones of the remote station including means producingcontrol voltages dependent on the quantityto be metered, meteringreceiving means at corresponding control points at the dispatchingoi'lice, means responsive to the selection of a control point at one ofthe remote stations having metering means associated therewith effectiveto effect connection of the transmitting means and the receiving meansin series circuit relation in the signal channel for continuouslyoperating the receiving means, and additional means responsive to theinitiation of a signal from a control pointother than a metering pointoperable to shunt the transmitting and receiving means from the signalchannel while said other control point operates. i

t 6. In a supervisory control system having a dispatching ofiice and aplurality of remote stations each with supervisory control sending andreceiving equipment connected in series circuit relation by a commonsignal channel and provided with a plurality of control points, meteringtransmitting means associated with certain of the pointsat the remotestations, metering receiving means associated with the correspondingcontrol points at the dispatching oifice, means operable from thecontrol station over said corresponding control points to selectivelyconnect one of the metering transmitting means and its correspondingreceiving means at the dispatching ofiice in circuit relation with thesignal channel for a continuous metering operation, and means at thedispatching oifice interlocking the metering control points to preventinitiation of another metering operation While one metering operation istaking place.

signal channel.

8.111 a supervisory control system having supervisory control equipmentwith a plurality means at certain of the control points attwo ormore ofthe remote stations and metering receiving means at the correspondingcontrol points controllable to be connected in circuit with the signalchannel from the dispatching ofdce for continuous metering operation,relay means responsive to the initiation of a supervisory or controlsignal operable to effectively disconnect the metering transmitting andreceiving means from the channel and. restore the signal'channel for asupervisory or control operation, and control means at saidcorresponding control points at the dispatching ohice operable toprevent initiation of a metering operation fromone of'said points Whilea metering operation'is taking place from another of said points.

9. In a supervisory control system supervising i control sending andreceiving means with corre- 1 control points arranged to be connected incircuit relation with their respective transmitters, means at thedispatching office andeach of the,

remote stations operable in response to the initiae tion of asupervisory or control function from any 7 of the other control pointsto effectively disconnect the metering transmitters and receivers fromthe signal channel, and circuit means at the dis WILLARD A. DERR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,394,642 Quass Oct. 25, 1921,682,049 Meyers Aug. 28, 1928 2,011,237 Baughman Aug. 13, 1935 2,059,204Boswau Nov. 3, 1936 2,259,573 Lewis Oct. 21, 1941 2,314,692 Derr Mar.23, 1943 2,327,25 Derr Aug. 17, 1943 2,431,631 Baughman Nov. 25, 1947

